This page discusses unusual visual phenomenon such as floaters and different types of flashing lights. Other visual abnormalities such as seeing rainbows around lights, abnormal color vision, and distorted vision are discussed as well.

Floaters and Flashing Lights

"Floater" is a common term referring to seeing abnormal spots moving in the vision. It is important to be careful and very specific in how this is described as the description itself can help lead to the proper diagnosis. Some people use the phrase, "I feel like there is something moving in my eye". However, this phrase could also be used to describe the physical sensation of something irritating the surface of the eye (a foreign body sensation), and if the meaning of this phrase is not clarified, the wrong diagnosis could be made.

Many people are born with "floaters" that they see from time to time, especially when looking at a blank background or laying back looking at a bright daytime sky. What is being seen in this case is most likely the remnant of a vessel that existed between the optic nerve and lens of the eye before birth, which degenerates into a nearly transparent "worm-like" opacity that moves about in the vitreous. People that have this normal variation are generally familiar with its appearance to them, and it usually changes very little throughout life.

A change in floaters or a new floater is reason for concern, as it can be associated with disease conditions within the eye, especially if associated with flashes of light. These new floaters might also be nearly transparent, but they may appear more like gnats or insects flying in the vision or crawling on the floor. Sometimes they are described like cobwebs in the vision. The examining doctor can often actually visualize what the new floater is during an eye examination. Note that something floating in the tear film of the eye or a foreign body on the surface of the eye will not be visualized as a floater (although it might blur the vision). Similarly, except in cases of severe trauma, objects cannot enter the eye from the outside to cause floaters.

"Flashing" is a symptom of seeing a flash of light in the vision. This is rarely seen as a normal visual phenomenon throughout life. It is important to distinguish the nature of the flash, as one type of flash is very brief and transient, like a lightning bolt, and other flashes are more continuous and can last for minutes or hours. Sometimes flashing might also be seen with head or eye movement. Sometimes after cataract surgery with lens implants, light might strike the lens implant at a certain angle that might cause a flash in the peripheral vision, and sometimes light might strike a lens implant in such a way that it can appear reflective to another person looking at the pupil of the eye.

Vitreous Detachment

The vitreous is a gel-like fluid which fills most of the eye. As people age, this vitreous becomes more and more liquefied. The vitreous has loose attachments to the retina, and more firm attachments to the optic nerve. At some point in a person's life, the vitreous liquefies enough to shift position in the eye. When this occurs, usually between age 50 and 70, the back edge of the vitreous will pull forward away from the optic nerve and retina, leading to a "posterior vitreous detachment". This is generally a normal process, although it may happen abnormally early in cases of high nearsightedness or trauma. As the vitreous detaches, it tugs on the retina and optic nerve. This is perceived as a flash of light, similar to a lightning flash in the corner of the vision. It may occur especially with eye movement, since the vitreous moves in the eye. Debris pulled off of the optic nerve and retina are then seen as floaters, suspended in the vitreous above the retina. Sometimes this is described as a cobweb, a net, a string, or a fly over the vision.

These symptoms usually resolve over a period of days to weeks, although some people will continue to see the floaters for a longer period of time. The important thing is to determine that the retina is healthy as the vitreous detaches. This requires a careful dilated examination of the retina to look for tears, or other areas which may be at risk for tearing. A retinal tear can then lead to retinal detachment, if not treated. Thus, people experiencing these symptoms should be examined by an ophthalmologist as soon as possible. (Note, only about 1 in 10,000 cases of vitreous detachment lead to retinal detachment, but it still is one of the most common causes of retinal detachment.) It has been found that the second eye will also develop a vitreous detachment within 1-2 years of the first eye, and this should be examined as well when it happens.

Retinal Tear

A tear in the retina can occur with vitreous detachment (see discussion above), with trauma or eye injury, or in areas at risk for a retinal tear, such as "lattice degeneration". The symptoms of a retinal tear usually are of a flash of light in the peripheral vision followed by floaters. The floaters may be debris, but may also be blood, if the tear extends through a retinal blood vessel. Blood in the vitreous is often perceived as millions of tiny floaters, or actual blobs in the vision if the hemorrhage is more significant. Symptomatic retinal tears should be treated by laser to prevent retinal detachment. Sometimes a retinal tear is discovered incidentally as part of an eye examination. These may or may not need to be treated.

Uveits (inflammation in the eye)

Uveitis refers to a large group of disorders which cause inflammation within the eye. A similar condition, iritis, usually refers to inflammation involving the front structures of the eye associated with pain, redness, and sensitivity to light. In this discussion, uveitis could also have these symptoms, but mainly consists of inflammation involving the back structures of the eye (the retina, choroid, and optic nerve). Inflammatory debris liberated into the vitreous leads to the visualization of floaters. If this liberation continues, the vision may become substantially hazy and blurred.

Entoptic Phenomenon

Entoptic phenomenon is a normal phenomenon that some people may become suddenly aware of. This sudden awareness may lead to the idea that there is a problem with the eyes, when actually there is not. The entoptic phenomenon can be seen especially when looking at a bright blue sky. Small, rapid pin-point sparks of light can be seen darting about in the central vision. Some people may think that these sparks are floaters. In reality, they may represent white blood cells moving through the blood capillaries of the retina. This is a normal finding, and actually indicate normal retinal function.

Eales' Disease

Eales' Disease is a rare disorder primarily affecting young adult males in their 30's to 50's. 80% of those affected are male, and usually both eyes are affected. There is no known cause for the disease, and no known association with any medical disorder (although one study noted balance dysfunction and hearing loss in 24% of patients).

In Eales' Disease, there is inflammation of the retinal vessels, where there is visible sheathing of the vessels and inflammation of the vessels. This can lead to obstruction of the vessels, hemorrhages into the retina and vitreous, and occasionally retinal detachment (in severe cases). There may be no symptoms of this disease, or one may see floaters, or develop a loss of vision if vitreous hemorrhage or retinal detachment occur.

Treatment is usually aimed at eliminating the risk of hemorrhage through retinal laser treatments. Oral anti-inflammatory agents may also be helpful.

Other Visual Phenomena:

Migraine headaches may be preceded by a visual "aura", lasting for 5 to 30 minutes (most commonly around 15 minutes), and then proceeding to the headache. Some people, however, experience the aura but do not have a headache. This visual aura can be very dramatic. Classically, a small blind spot appears in the central vision with a shimmering, zig-zag flicker light inside of it ("scintillating scotoma"). This enlarges, and moves to one side or the other of the vision, over the 5 to 30 minute period. When it is large, this crescent shaped blind spot containing this brightly flashing light can be difficult to ignore, and some people fear that they are having a stroke. In reality, it is generally a harmless phenomenon (with one exception noted below), although many people subsequently get the migraine headache. Since migraine originates in the brain, the visual effect typically involves the same side of vision in each eye, although it may seem more prominent in one eye or the other. It is usually mainly perceived as occurring in the eye in which is occupies the temporal (outside) field of vision. The visual phenomenon would also be perceived in the nasal field of vision of the other eye.

Some people get different variations of this phenomenon, with the central vision being involved, or with the visual effect similar to "heat rising off of a car". Some people describe a "kaleidoscope" effect, with pieces of the vision being missing. All of these variations are consistent with ophthalmic migraine. There are many examples of "visual migraine" that have been drawn by patients available on the internet.

Please note that this is different from a condition known as "retinal migraine". A retinal migraine is a spasm of the artery entering the eye and leads to a temporary near-total loss of vision (a black out of the vision). This is different from "visual migraine", which originates from the brain and is perceived bilaterally in the vision.

A possible risk factor in women for stroke: Recent studies have found that women especially under age 45 with recent onset of probable migraine with visual symptoms (within the prior year) were almost seven times more likely to have a stroke compared to women with no history of migraine. In addition, women who also smoked and used oral contraceptives had seven times the risk of stroke than women who had probable migraine with visual symptoms alone. Read more about this study here.

Transient Visual Obscurations

A transient visual obscuration is a temporary or fleeting dimming of vision that can affect one or both eyes. It differs from Amaurosis fugax, which is a more substantial black-out of some or all of the vision for a longer period of time.

Transient visual obscurations have been associated with increased intracranial pressure, specifically Idiopathic Intracranial Hypertension. This condition also has symptoms of headache and sometimes double vision.

In multiple sclerosis, some people will have a transient decline in vision related to exercise or increased body temperature, such as from bathing in a hot tub. This is known as Uhthoff's phenomenon.

In some cases of vertebral artery insufficiency or obstruction, people will experience transient dimming of the vision, often with a sensation of imbalance.

In cases of orthostatic hypotension, there can be a drop in cerebral blood flow associated with standing rapidly from a seated or lying position. This can lead to a transient dimming of vision with a sensation of imbalance or syncope. Some anti-hypertensive medications can worsen this symptom.

Some cases or transient visual obscurations have occurred after consuming a very heavy meal, or after sexual intercourse.

Rainbow Vision

Seeing rainbows around lights, especially at night, usually indicates swelling of the cornea. This may occur from a variety of causes which are discussed under Corneal Edema. Cataract can sometimes cause this also.

Abnormal Color Vision

Color vision is perceived mainly by the macula, which is the central vision portion of the retina. Thus any disorder affecting the macula may cause a disturbance in color vision. However, about 8% of males and 0.5% of females have some version of "color blindness" from birth. Usually this is an genetically inherited trait, and is of the "red-green confusion" variety. The reds, browns, olives, and golds may be confused. Purple may be confused with blue, and pastel pinks, oranges, yellows, and greens look similar. Usually both eyes are affected equally.

There are many rare macular retinal disorders that can lead to a loss of color vision, and many of these syndromes are inherited as well. There may also be a problem with a generalized loss of vision with these problems as well. Other retinal problems can lead to a temporary disturbance of color vision, such as Central serous Chorioretinopathy, Macular Edema of different causes, and Macular Degeneration.

Certain types of cataract can gradually affect the color vision, but this is usually not noticed until one cataract is removed. The cataract seems to filter out the color blue, and everything appears to be more blue after cataract extraction. Optic nerve disorders such as Optic Neuritis can greatly affect color vision, with colors seeming washed out during or after an episode, especially the color red.

Distorted Vision

Distortion of vision refers to straight lines not appearing straight, but instead bent, crooked, or wavy. Usually this is caused by distortion of the retina itself. This distortion can herald a loss of vision in macular degeneration, so anyone with distorted vision should seek medical attention by an ophthalmologist promptly. Other conditions leading to swelling of the retina can cause this distortion, such as Macular edema and Central serous Chorioretinopathy.

An "Amsler grid" can be supplied by an ophthalmologist so that the vision can be monitored for distortion in people who may be predisposed to this problem.

Tunnel Vision

"Tunnel vision" implies that the peripheral vision, or side vision, is lost, while the central vision remains. Thus, the vision is like looking through a tunnel, or through a paper towel roll. Some disorders that can cause this include:

Glaucoma - severe glaucoma can result in loss of nearly all of the peripheral vision, with a small "island" of central vision remaining. Sometimes even this island of vision can be lost as well.

Other Optic Nerve Conditions - There are a number of sometimes hereditary optic nerve conditions that can lead to a severe decrease in peripheral vision. Often both eyes are affected, and the patient's visual impairment may be severe enough to require assistance with ambulation (cane, service dog). In some cases the central vision can still be normal in spite of the peripheral vision loss.

In some cases extensive laser photocoagulation is required to treat vascular conditions of the eye such as proliferative diabetic retinopathy and central retinal vein occlusions. This often leads to a near total loss of peripheral vision with sparing of the central vision. This can also occur as a complication of the disease processes themselves, due to a loss of retinal blood supply.

Following retinal detachment surgery there are many cases where there may be a significant loss of peripheral vision.

Stroke - a stroke involving both sides of the visual part of the brain may eliminate nearly all of the peripheral vision. Fortunately, this is a very rare occurrence

Retinitis pigmentosa (see below)

Retinitis pigmentosa

Retinitis pigmentosa is usually a hereditary disorder which can be part of numerous syndromes. It is more common in males. The peripheral retina develops pigmentary deposits, and the peripheral vision gradually becomes worse and worse, leading to "tunnel vision". The central vision can be affected eventually as well. People with this problem may have trouble getting around in the dark. Cataract can be a complication as well. There is no known treatment for this disorder, and supplements of Vitamin A have not been proven to help.